Frequency Multiplexed Optical Touchscreen for Fast Response
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Solution Overview
Problem
Conventional infrared (IR) touch panels face challenges in achieving fast response times and minimizing costs for large-sized touch panels, as they typically require sequential activation of LEDs, which complicates the detection of two-dimensional coordinate information.
Innovation Solution
A frequency multiplexed touch system with multiple LEDs at different edges of the touch panel, where the intensity of light emitted from each LED is modulated with varying frequencies, allowing simultaneous detection of touch events using optical receivers and processor circuitry to determine the location based on attenuation factors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If sequential activation of LEDs is used in conventional IR touch panels, then the system can detect touch events, but the response time becomes slow and the complexity increases for large-sized panels
Solution Approach 1:
The patent applies periodic action by modulating each LED with a specific modulation frequency and activating groups of LEDs in sequential time slots. Each LED emits light at its assigned frequency during its designated time slot, creating periodic signals that can be detected and decoded to determine touch location. This approach enables multiple LEDs to be effectively utilized simultaneously while maintaining manageable system complexity through frequency and time multiplexing.
2Productivity
If multiple LEDs are activated simultaneously to improve response time, then the detection speed increases, but the complexity of detecting two-dimensional coordinate information increases
Solution Approach 1:
The patent changes parameters by assigning unique modulation frequencies to different LEDs and organizing them into groups along X and Y axes. The system varies the activation time slots and modulation frequencies as key parameters, allowing the optical receiver to decode which specific LEDs were blocked by a touch. This parameter variation enables simultaneous activation of multiple LEDs while maintaining the ability to resolve two-dimensional coordinate information through frequency and temporal analysis.
3Ease of operation
If only one LED is activated at a time to reduce complexity, then the system is easier to control, but the response time becomes too slow for large touch panels
Solution Approach 1:
The patent segments the LED array into multiple groups arranged along X and Y axes, with each group assigned specific modulation frequencies and time slots. This segmentation allows the system to activate multiple LEDs in parallel within each time slot while maintaining organized control structures. The segmentation enables faster scanning of the touch panel surface without overwhelming the control system, as each segment can be managed independently through its assigned frequencies and time windows.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables efficient and cost-effective detection of touch events on large touch panels by simultaneously using multiple LEDs with different frequencies, improving response time and reducing the complexity of coordinate detection.
Implementation Method 1
a first plurality of radiation sources that are located at a first edge of the touch panel, and a second plurality of radiation sources that are located at the first edge of the touch panel
Implementation Method 2
The intensity of light emitted from each of the first and second plurality of radiation sources is modulated with a modulation frequency from a set of frequencies utilized repetitively in varying order between the first and the second plurality of radiation sources
Implementation Method 3
an optical receiver that is located at a second edge of the touch panel and is configured to receive the light emitted from each of the first and second plurality of radiation sources
Implementation Method 4
performing a frequency transform on the digital signal and determining an amplitude of the frequency transformed signal for each of the respective modulation frequencies
Data Source
AI summary
An apparatus, methods, systems, and computer program products are provided that can detect touch events on touch panels in a more effective and less costly manner. According to an embodiment, a touch system includes a touch panel and a plurality of radiation sources located at a first edge of the touch panel. The intensity of light emitted from each of the plurality of radiation sources is modulated with a respective modulation frequency. The touch system further includes an optical receiver that is located at a second edge of the touch panel and is configured to receive the light emitted from each of the plurality of radiation sources.